fix(docs): use relearn notice shortcode instead of unsupported alert (#10206)

The Hugo relearn theme does not provide an "alert" shortcode, so the
docs deploy failed at the Build site step:

  failed to extract shortcode: template for shortcode "alert" not found
  docs/content/features/distributed-mode.md:136

Convert the warning block to the theme-supported notice shortcode used
everywhere else in the docs.

Signed-off-by: Ettore Di Giacinto <mudler@localai.io>
Co-authored-by: Ettore Di Giacinto <mudler@localai.io>

docs/content/features/distributed-mode.md

@@ -133,9 +133,9 @@ When S3 is not configured, model files are transferred directly from the fronten
 
 For high-throughput or very large model files, S3 can be more efficient since it avoids streaming through the frontend.
 
-{{% alert icon="⚠️" color="warning" %}}
+{{% notice warning %}}
 The worker HTTP file transfer server is authenticated by `LOCALAI_REGISTRATION_TOKEN`. If the token is **empty**, the server **fails open** — anyone who can reach the port gets read/write access to the worker's models/staging/data directories (a remote model-poisoning / exfiltration vector). The worker logs a loud warning at startup in this case. Always set `LOCALAI_REGISTRATION_TOKEN` in distributed mode, and set `LOCALAI_DISTRIBUTED_REQUIRE_AUTH=true` (frontend **and** workers) to make a missing token *or* missing NATS credentials a hard startup error rather than a silent fail-open. Firewall the file-transfer port (gRPC base − 1) so only the frontend can reach it.
-{{% /alert %}}
+{{% /notice %}}
 
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